java.lang.NoClassDefFoundError: org/aopalliance/intercept/MethodInterceptor

When we try to implement the Spring AOP,we may get this exception -"org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/aopalliance/intercept/MethodInterceptor".
 
The full exception stacktrace will look like below:

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.aop.config.internalAutoProxyCreator': Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/aopalliance/intercept/MethodInterceptor

            at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:965)

            at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:911)

            at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)

            at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)

            at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)

            at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)

            at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)

            at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)

            at org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:728)

            at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:449)

            at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139)

            at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:93)

            at aspect.AspectTest.main(AspectTest.java:10)

Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: org/aopalliance/intercept/MethodInterceptor

            at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:162)

            at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:76)

            at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:958)

            ... 12 more

Caused by: java.lang.NoClassDefFoundError: org/aopalliance/intercept/MethodInterceptor

            at org.springframework.aop.framework.adapter.DefaultAdvisorAdapterRegistry.(DefaultAdvisorAdapterRegistry.java:49)

            at org.springframework.aop.framework.adapter.GlobalAdvisorAdapterRegistry.(GlobalAdvisorAdapterRegistry.java:31)

            at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.(AbstractAutoProxyCreator.java:118)

            at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.(AbstractAdvisorAutoProxyCreator.java:47)

            at org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator.(AspectJAwareAdvisorAutoProxyCreator.java:46)

            at org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator.(AnnotationAwareAspectJAutoProxyCreator.java:48)

            at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

            at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)

            at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)

            at java.lang.reflect.Constructor.newInstance(Unknown Source)

            at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)

            ... 14 more

Caused by: java.lang.ClassNotFoundException: org.aopalliance.intercept.MethodInterceptor

            at java.net.URLClassLoader$1.run(Unknown Source)

            at java.net.URLClassLoader$1.run(Unknown Source)

            at java.security.AccessController.doPrivileged(Native Method)

            at java.net.URLClassLoader.findClass(Unknown Source)

            at java.lang.ClassLoader.loadClass(Unknown Source)

            at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)

            at java.lang.ClassLoader.loadClass(Unknown Source)

            ... 25 more

This exception will be thrown if we don't have the aopalliance.jar in the class path and make sure to add the same to your project classpath.You can download the aopalliance.jar from the spring  official site here.